Electron microscope

ABSTRACT

An object of the present invention is to provide an electron microscope that is capable of improving work efficiency when restarting sample observation. A control unit for controlling observation-condition setting devices, which include an electron-gun control unit, an irradiation-lens control unit, an objective-lens control unit, a magnifying-lens-system control unit, and a sample-stage control unit, is provided. When image data of a certain sample is specified, observation condition data of the sample is retrieved. Then, observation conditions, which are the same as those used when the image data of the sample has been saved, are automatically restored on an electron microscope on the basis of the observation condition data. As a result, an image, which is the same as the stored image, is restored faithfully.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an electron microscope that usesa method by which observation result of a sample is stored as imagedata, and more particularly to an electron microscope that is suitablefor use in repetitive observation of the same sample.

[0002] In observation of a sample using an electron microscopes it isnecessary to set observation conditions such as magnification,acceleration voltage of an electron beam, and an observation mode, whichare suitable for observation of the sample, before starting theobservation.

[0003] In this case, these observation conditions are set by devicesthat are generically called observation-condition setting devices suchas a device for controlling an electron gun, a device for controlling anirradiation lens, a device for controlling an objective lens, a devicefor controlling a magnifying lens system, and a device for controlling asample stage.

[0004] These observation conditions are a part of information that isindispensable to evaluation of the observation result of the sample.Therefore, when saving an image, it is desirable to save observationconditions of the recorded image together with the image.

[0005] In this connection, when recording the observation resultobtained by the electron microscope as an image, either of the followingmethods is generally conventionally used; a method in which theobservation result is saved in an image recording medium, such as aphotographic film, as a real image; and a method in which theobservation result is saved in a memory as image data by a TV camera(Television Camera).

[0006] With both of the methods described above, it is possible torecord the observation conditions together with the recorded image.However, if the observation conditions are recorded on a film, it isdifficult to record all observation conditions because a writing area islimited. On the other hand, in the case of the image data by a TVcamera, there is no hard problem of a writing area. Therefore, theobservation conditions can also be displayed immediately in real timetogether with the image.

[0007] In the prior art, for example, while observing a certain sample,if the observation is interrupted for some reason, but an operator triesto start the observation again, the following operation is required:displaying observation conditions together with an image using therecording method for image data; and while watching the displayedobservation conditions, providing an electron microscope with eachcondition setting by manual operation with reference to the observationconditions.

[0008] The prior art described above has a problem in work efficiencybecause settings of the observation conditions when restarting theobservation are not taken into consideration.

[0009] As described above, when using an electron microscope, it isnecessary to set desired observation conditions in response to a sampleto be observed. This requires considerably complicated work.

[0010] The reason why complicated work is required for the settings ofthe observation conditions is that as described above, the observationconditions cover a wide variety of conditions: that is to say, inaddition to magnification and acceleration voltage, there are manyobservation modes including, for example, a diffraction mode, a highresolution mode, a high contrast mode, and an extremely lowmagnification mode.

[0011] When starting observation of a certain sample, it is natural thatcomplicated work is required. In other words, it is unavoidable.However, in the prior art, even if the same sample is observed, settingsof the observation conditions by manual operation is required for eachobservation-condition setting device every time the work is started.This causes work efficiency to be decreased.

SUMMARY OF THE INVENTION

[0012] An object of the present invention is to provide an electronmicroscope that is capable of improving work efficiency when restartingobservation of the sample.

[0013] According to an aspect of the present invention, the objectdescribed above can be achieved by an electron microscope using a methodby which observation condition data of a sample is saved while theobservation condition data is associated with image data of the sampleso that both data are in a one-to-one correspondence, the microscopecomprising; a control means for controlling an observation-conditionsetting means of the electron microscope is provided; wherein when imagedata of a certain sample is specified, the control means retrievesobservation condition data of the sample; and on the basis of theobservation condition data retrieved, the control means controls theobservation-condition setting means so that observation conditionscorrespond to the same as those used when the image data of the samplewas saved.

[0014] The image data may be saved as TIF format data that includes atag area: and the observation condition data may be saved in the tagarea. In like manner, in addition to magnification and accelerationvoltage as the observation conditions, the observation conditions mayalso include one of observation modes, that is to say, one of adiffraction mode, a high resolution mode, a high contrast mode, and anextremely low magnification mode. Moreover, the observation conditionsmay also include at least a coordinate position of a sample stage.

[0015] According to the present invention, a recorded image can beassociated with observation conditions of the Image completely. Inaddition, the observation conditions as feedback are automatically givento the electron microscope concurrently with displaying of the recordedimage. Therefore, it is possible to faithfully restore the recordedimage on the electron microscope with ease.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects, features and advantages of thepresent invention will become more apparent from the followingdescription taken in connection with the accompanying drawings, inwhich:

[0017]FIG. 1 is a schematic configuration diagram illustrating oneembodiment of an electron microscope according to the present invention;and

[0018]FIG. 2 is a flowchart illustrating operation in one embodimentaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] An electron microscope of an embodiment according to the presentinvention, which is shown in FIG. 1, will be described in detail asbelow.

[0020]FIG. 1 is one embodiment in which the present invention is appliedto a transmission electron microscope, As described in the figure, anelectron gun 2 is mounted on the upper end (in the figure) of anelectron-microscope main body 1. It is so devised that an irradiationlens 4 irradiates a sample S held on a sample stage 5 with an electronbeam B that is emitted by this electron gun 2.

[0021] Then, the electron beam B, which has been transmitted throughthis sample S, is magnified by an objective lens 6 and a magnifying lenssystem 7 before the magnified electron beam B is projected on a TVcamera 8. In this case, the electron gun 2 is controlled by anelectron-gun control unit 11; the irradiation lens 4, the objective lens6, and the magnifying lens system 7 are controlled by anirradiation-lens control unit 12, an objective-lens control unit 13, anda magnifying-lens-system control unit 14 respectively; and the samplestage 5 is controlled by a sample-stage control unit 15.

[0022] Therefore, these devices, that is to say, the electron-guncontrol unit 11, the irradiation-lens control unit 12, theobjective-lens control unit 13, the magnifying-lens-system control unit14, and the sample-stage control unit 15, serve as observation-conditionsetting devices.

[0023] The TV camera 8 comprises a scintillator plate, and an imagepickup device such as CCD. The TV camera 8 converts the electron beam B,which is projected on the image pickup element, into light to detect asignal on a pixel basis. Then, the TV camera 8 supplies the detectedsignal to a TV-camera control unit 16 to convert the signal into atime-series image signal. After that, this image signal is supplied to amonitor 17 where the image signal is displayed as an image. In addition,the same image signal, which has been output from the TV-camera controlunit 16, is also supplied to a control unit 11 where the image signal isstored and saved in a memory as image data.

[0024] A lower end portion of the electron-microscope main body 1 formsa camera chamber 9, in which a fluorescent plate 10 is mounted.Therefore, using a mechanism, which is not illustrated in the figure, toremove the TV camera 8 from a path of the electron beam B enables us toobserve an enlarged image of the sample S, which is obtained by theelectron beam B, on a surface of the fluorescent plate 10.

[0025] By the way, the configuration described above is not so differentfrom that of a general electron microscope. However, the presentinvention is largely different from the prior art on the followingpoint: in this embodiment, each of the observation-condition settingdevices of the electron microscope, that is to say, the electron-guncontrol unit 11, the irradiation-lens control unit 12, theobjective-lens control unit 13, the magnifying-lens-system control unit14, and the sample-stage control unit 15, are coupled to the controlunit 18 through a predetermined transmission line in order to permitdata to be transmitted and received mutually, with the result that thecontrol unit 18 can set observation conditions.

[0026] Because of it, the control unit 18 is configured to have, forexample, a computer into which a predetermined program is loaded. Thisenables generation of control data that is required to control theobservation-condition setting devices by supplying the control data tothe devices.

[0027] In the next place, operation will be described with reference toa flowchart in FIG. 2. To begin with, in this embodiment, two kinds ofprocessing, that is to say, “image record processing” and “imageretrieval processing”, are executed by the control unit 18.

[0028] In this case, the “image record processing” is processing usedwhen a certain desired sample is observed. On the other hand, the “imageretrieval processing” is processing used for the following case: afterthe observation of the certain desired sample is finished, the same partof the sample image for the same sample is restored for observationusing the same observation conditions as those in the previousobservation.

[0029] In the flowchart shown in FIG. 2, processing A2 through A4, whichfollows processing A1, is the image record processing; and processing A6through A9, which follows processing A5, is the image retrievalprocessing. The processing is executed by the control unit 18 accordingto an instruction from an operator.

[0030] First of all, the “image record processing” will be described. Inthe beginning, the operator prepares a sample S as an observationtarget, and then operates the electron microscope to set predeterminedobservation conditions so that an enlarged image of a predetermined partof the sample S is picked up by the TV camera S. In this case, theoperator operates the electron microscope while watching the enlargedimage of the sample S displayed in the monitor 17. The operator maywatch an image in the fluorescent plate 10 as a matter of course.

[0031] Operation for this case is not shown in FIG. 1. The operation isperformed using a predetermined input device such as a keyboard forexample. Predetermined control data is input into the electron-guncontrol unit 11, the irradiation-lens control unit 12, theobjective-lens control unit 13, and the magnifying-lens-system controlunit 14 so that desired acceleration voltage and magnification, and adesired observation mode, can be obtained.

[0032] In addition to it, control data is also inputted into thesample-stage control unit 15 in order to move the sample stage 5 so thata desired part of the sample S comes into a field of view forobservation. As a result, an image corresponding to the desired part(coordinates) is obtained for the desired sample S on the basis of thedesired observation conditions.

[0033] Therefore, if the processing ends here, the processing is thesame as that for the case of observation using a general electronmicroscope. However, in this embodiment, after the image correspondingto the desired part is obtained for the desired sample S on the basis ofthe desired observation conditions, the operator executes predeterminedoperation required to instruct the control unit 18 to record this image(step A1). It is to be noted that the operation is also performed usinga predetermined input device such as a keyboard.

[0034] After that, to begin with, the control unit 18 converts an imagesignal, which has been captured from the TV camera 8, into data in TIFformat (TIFF) (step A2). Then, the image data, which has been convertedinto the TIF format, is stored and saved in a memory (step A3).

[0035] On the other hand, in parallel with the save of this image data,the control unit 18 captures observation conditions of the image as datafrom the electron-gun control unit 11, the irradiation-lens control unit12, the objective-lens control unit 13, and the magnifying lens controlunit 14. In addition, a coordinate position of the sample S beingobserved is also captured as data from the sample-stage control unit 15.

[0036] Then, data, which expresses these observation conditions and thecoordinate position, is stored in a tag area in TIF format as tag dataof the image data (step A4). Therefore, according to this embodiment, asa result of execution of the “image record processing”, when a certaindesired sample is observed, observation conditions of the image areentirely stored and saved in the tag area in TIF format together withthe image data.

[0037] As a result of the processing described above, after observingthe certain sample, reading its image data permits the observationconditions of the image to be read as data together with the image data.

[0038] Next, the “image retrieval processing” will be described. Theimage retrieval processing is started by the following operator'soperation: selecting a certain desired sample: mounting the selectedsample on the sample stage 5 as the sample S: and inputting apredetermined instruction into a control unit 18. In this case, thepredetermined instruction specifies the image data, which has alreadybeen saved as TIF format by the image record processing described above,relating to the selected sample S.

[0039] Therefore, the image retrieval processing can be performed onlywhen image data of the desired sample has already been saved in TIFformat by the image record processing. Such a situation includes, forexample, the following case: while observing a certain sample, theobservation is interrupted for some reason, and then the observation ofthe same sample is started again.

[0040] In this manner, when the image retrieval processing is started,image data of the specified sample is retrieved by the control unit 18(step A5). After that, the control unit 18 supplies this image data tothe monitor 17 to display the saved observation image on a monitorscreen (step A6). As a result of it, the operator can check whether ornot desired image data has been retrieved correctly. In this case,observation conditions and a coordinate position of the correspondingsample are additionally saved in the tag area of the image data in TIFformat as tag data.

[0041] Then, the control unit 18 reads the tag data from the image data(step A7), and supplies data expressing observation conditions, such asacceleration voltage and magnification, in this tag data to theelectron-gun control unit 11 and to each of lens control units 12through 14 as feedback for control (step A8).

[0042] To be more specific, each corresponding control data in the tagdata is inputted into each of the electron-gun control unit 11, theirradiation-lens control unit 12, the objective-lens control unit 13,and the magnifying-lens-system control unit 14. The control unitscontrol each element so that acceleration voltage and magnification,which are specified by the tag data, are obtained, and an observationmode (for example, a diffraction mode, a high resolution mode, a highcontrast mode, and an extremely low magnification mode) is alsoobtained.

[0043] In addition, the data expressing a coordinate position in the tagdata is supplied to the sample-stage control unit 15 to provide feedback for control In a similar manner (step A9). To be more specific, thecoordinate position data in the tag data is inputted into thesample-stage control unit 15 to move the sample stage 5 so that a partspecified by the tag data of the sample S comes into a field of view forobservation.

[0044] As a result of it, in the case of this embodiment, specifyingimage data of the sample permits the electron microscope to beautomatically set in the same observation conditions as those used whenthe image data of the sample has been saved. In addition, the samplestage 5 is also automatically set at the same coordinate position.

[0045] Therefore, according to this embodiment, for example, even ifobservation of the sample S is interrupted for some reason, when theobservation of the same sample S is started again after that, it ispossible to restore a state of the electron microscope automaticallyimmediately; in this case, the state is the same as that at the time ofthe interruption. As a result, the observation can be performed withefficiency.

[0046] In the prior art, for example, observation conditions are storedwhile the observation conditions are linked to a stored locationcorresponding to image data of a predetermined holder. However, if theimage is moved to another PC (personal computer) or another recordingmedium, the link data is separated. As a result, it is substantiallyimpossible to retrieve the observation conditions from the image.

[0047] However, since in the embodiment described above image data isconverted into data in TIF format, and observation conditions are storedin a tag area, corresponding observation conditions are always savedwithout fail. In addition to it, retrieving image data permitscorresponding observation condition data to be obtained at the sametime. Moreover, since there is no strict limitation of the quantity ofdata that can be saved, it is easy to completely restore observationconditions.

[0048] Although the embodiment described above relates to the case wherethe present invention is applied to the transmission electronmicroscope, it is needless to say that the present Invention can beapplied to the other electron microscopes such as a scanning electronmicroscope, for example. In the case of the scanning electronmicroscope, instead of saving coordinate position data of the samplestage, coordinate data measured when irradiating a sample surface withan electron beam is stored, and thereafter feedback is given to anelectron beam scanning control unit.

[0049] Although the invention has been described in its preferredembodiments with a certain degree of particularity, obviously manychanges and variations are possible therein. It is therefore to beunderstood that the present invention may be practiced otherwise than asspecifically described herein without departing from the scope andspirit thereof.

What is claimed is:
 1. An electron microscope using a method by whichobservation condition data of a sample is saved while the observationcondition data is associated with image data of the sample so that bothdata are in a one-to-one correspondence, said microscope comprising: acontrol means for controlling an observation-condition setting means ofthe electron microscope is provided; wherein when image data of acertain sample is specified, the control means retrieves observationcondition data of the sample; and on the basis of the observationcondition data retrieved, the control means controls theobservation-condition setting means so that at observation conditionscorrespond to the same as those used when the image data of the samplewas saved.
 2. An electron microscope according to claim 1, wherein: saidimage data is saved as TIF format data that includes a tag area; andsaid observation condition data is saved in the tag area.
 3. An electronmicroscope according to claim 1, wherein; said observation conditionsinclude not only magnification and acceleration voltage but also anobservation mode, and the observation mode is one of a diffraction mode,a high resolution made, a high contrast mode, and an extremely lowmagnification mode.
 4. An electron microscope according to claim 1,wherein: said observation conditions include at least a coordinateposition of a sample stage.